Fibroblast growth factors are large polypeptides widely expressed in developing and adult tissues (Baird et al., Cancer Cells, 3:239-243, 1991) and play crucial roles in multiple physiological functions including angiogenesis, mitogenesis, pattern formation, cellular differentiation, metabolic regulation and repair of tissue injury (McKeehan et al., Prog. Nucleic Acid Res. Mol. Biol. 59:135-176, 1998; Burgess, W. H. et al., Annu Rev. Biochem. 58:575-606 (1989). The prototypic fibroblast growth factors (FGFs), FGF-1 and FGF-2, were originally isolated from brain and pituitary as mitogens for fibroblasts. FGF-3 was identified to be a common target for activation by the mouse mammary tumor virus (Dickson et al., Ann. N.Y. Acad. Sci. 638:18-26 (1991); FGF-4 to FGF-6 were identified as oncogene products (Yoshida et al., Ann. NY Acad. Sci. 638:27-37 (1991); Goldfarb et al., Ann. NY Acad. Sci 638:38-52 (1991); Coulier et al., Ann. NY Acad. Sci. 638:53-61 (1991)). FGF-10 was identified from rat lung by homology-based polymerase chain reaction (PCR) (Yamasaki et al., J. Biol. Chem. 271:15918-15921 (1996)). FGF-11 to FGF-14 (FGF homologous factors (FHFs) 1 to 4) were identified from human retina by a combination of random cDNA sequencing, database searches and homology-based PCR (Smallwood et al., Proc. Natl. Acad. Sci. USA 93:9850-9857 (1996)). FGF-15 was identified as a downstream target of a chimeric homeodomain oncoprotein (McWhirter et al., Development 124:3221-3232 (1997)). FGF-16, FGF-17, and FGF-18 were identified from rat heart and embryos by homology-based PCR, respectively (Miyake et al., Biochem. Biophys. Res. Commun. 243:148-152 (1998); Hoshikawa et al. Biochem. Biophys. Res. Commun. 244:187-191 (1998); Ohbayashi et al., J. Biol. Chem. 273:18161-18164 (1998)). FGF-19 was identified from human fetal brain by database search (Nishimura et al., Biochim. Biophys. Acta 1444:148-151 (1999)). They have a conserved ˜120-amino acid residue core with ˜30 to 60% amino acid identity.
Animal models, overexpression, and analysis of naturally occurring mutations implicate fibroblast growth factors and their receptors in a wide range of diseases (e.g. Wilkie et al., Current Biology, (1995) 5:500-507; Pugh-Humphreys et al, In: The Cytokine Handbook, A. Thomson ed, 2nd edition, Academic Press, Harcourt Brace & co. publishers, London, pp 525-566) suggesting that regulation of activity could be used for treatment. For example, inhibition of fibroblast growth factor-2 by the compound Suramin prevents neovascularisation and tumor growth in mice (Pesenti et al., British Journal of Cancer, 66:367-372). Fibroblast growth factors also function in angiogenesis (Lyons, M. K., et al., Brain Res. (1991) 558:315-320), wound healing (Uhl, E., et al., Br. J. Surg. (1993) 80:977-980, 1993), astrogliosis, glial cell proliferation and differentiation (Biagini, G. et al., Neurochem. Int. (1994) 25:17-24), cerebral vasodilation (Tanaka, R. et al., Stroke (1995) 26:2154-2159), and neurotrophic/neuromodulatory processes.
Fibroblast growth factor also has multiple positive effects including blood flow and protection from calcium toxicity to improve outcome in cerebral ischemia (Mattson, M. P. et al., Semin. Neurosci. (1993) 5:295-307; Doetrocj. W. D. et al., J. Neurotrauma (1996) 13:309-316). Basic FGF treatment promotes neoangiogenesis in ischemic myocardium (Schumacher et al., Circulation (1998) 97: 645-650). Basic FGF enhances functional recovery and promotes neuronal sprouting following focal cerebral infarct (Kawamata et al., Proc. Natl. Acad. Sci. (1997) 94 (15):8179-84). According to the published literature, the FGF family consists of at least twenty-two members (Reuss et al., Cell Tissue Res. 313:139-157 (2003)).
Fibroblast growth factor 21 (FGF-21) has been reported to be preferentially expressed in the liver (Nishimura et al., Biochimica et Biophysica Acta, 1492:203-206 (2000); WO 01/36640; and WO 01/18172, which are incorporated by reference herein) and described as a treatment for ischemic vascular disease, wound healing, and diseases associated with loss of pulmonary, bronchia or alvelor cells or function and numerous other disorders. FGF-21 is expressed primarily in liver, kidney, and muscle tissue (see Example 2 of US Patent Publication No. 20040259780 which is incorporated by reference herein in its entirety). The FGF-21 gene is composed of 3 exons and is located on chromosome 19. Unlike other FGFs, FGF-21 does not have proliferative and tumorigenic effects (Genome Biol. 2001; 2(3):REVIEWS3005).
US Patent Publication No. 20010012628, which is incorporated by reference in its entirety, describes a nucleotide and protein sequence for human FGF-21 (see SEQ ID NO: 1 and 2, respectively of US Patent Publication No. 20010012628). SEQ ID NO: 2 in the above-mentioned publication, referred to sbgFGF-19, is 209 amino acids in length and contains a 28 amino acid leader sequence at the N terminus. The human FGF-21 sequence presented as SEQ ID NO: 3 herein is the same sequence as SEQ ID NO: 2 of US Patent Publication No. 20010012628. This sequence has a single nucleotide polymorphism (SNP) with proline (P) at position 174, hereinafter referred to as the “209 amino acid P-form of FGF-21.”
U.S. Pat. No. 6,716,626, which is incorporated by reference herein in its entirety, discuss human FGF-21 and homologous proteins in other mammals, particularly mice and rats. Mouse FGF shown as SEQ ID NO: 1 of U.S. Pat. No. 6,716,626 was highly expressed in liver and expressed in the testis and thymus, and it was suggested that human FGF-21 may play a role in development of and recovery from liver disease and/or disorders of testicular function or function of cells derived from the thymus. SEQ ID NO: 4 of U.S. Pat. No. 6,716,626 is 209 amino acids in length and contains a 28 amino acid leader sequence at the N terminus. The human FGF-21 sequence presented as SEQ ID NO: 6 herein is the same sequence as SEQ ID NO: 4 of U.S. Pat. No. 6,716,626. This sequence has a single nucleotide polymorphism (SNP) with leucine (L) at position 174, hereinafter referred to as the “209 amino acid L-form of FGF-21.”
U.S. Patent Publication No. 20040259780, which is incorporated by reference herein in its entirety, discuss human FGF-21 and present a sequence that is 208 amino acids in length (SEQ ID NO: 2 of U.S. Patent Publication No. 20040259780) and contains a 27 amino acid leader sequence at the N terminus. The human FGF-21 sequence presented as SEQ ID NO: 7 herein is the same sequence as SEQ ID NO: 2 of U.S. Patent Publication No. 20040259780. This sequence has a single nucleotide polymorphism (SNP) with leucine (L) at position 173, herein after referred to as the “208 amino acid L-form of FGF-21.”
FGF-21 has been shown to stimulate glucose-uptake in mouse 3T3-L1 adipocytes in the presence and absence of insulin, and to decrease fed and fasting blood glucose, triglycerides, and glucagon levels in ob/ob and db/db mice and 8 week old ZDF rats in a dose-dependent manner, thus, providing the basis for the use of FGF-21 as a therapy for treating diabetes and obesity (WO 03/011213, which is incorporated by reference herein and Kharitonenkov et al. J Clin Invest. 2005 June; 115(6):1627-35). Kharitonenkov et al. J Clin Invest. 2005 June; 115(6):1627-35 also showed that transgenic mice expressing human FGF-21 are hypoglycemic, sensitive to insulin, and resistant to diet-induced obesity. Kharitonenkov et al. Endocrinology (in press) also show that FGF-21 lowered glucose, triglycerides, insulin, and glucagons in diabetic Rhesus monkeys.
In addition, FGF-21 has been shown to be effective in reducing the mortality and morbidity of critically ill patients (WO 03/059270, which is incorporated by reference herein). FGF-21 has been described in U.S. Patent Application 20050176631, which is incorporated by reference herein, to affect the overall metabolic state and may counter-act negative side-effects that can occur during the body's stress response to sepsis as well as systemic inflammatory response syndrome (SIRS) resulting from noninfectious pathologic causes. Thus, FGF-21 may be used to reduce the mortality and morbidity that occurs in critically ill patients. Critically ill patients include those patients who are physiologically unstable requiring continuous, coordinated physician, nursing, and respiratory care. This type of care necessitates paying particular attention to detail in order to provide constant surveillance and titration of therapy. Critically ill patients include those patients who are at risk for physiological decompensation and thus require constant monitoring such that the intensive care team can provide immediate intervention to prevent adverse occurrences. Critically ill patients have special needs for monitoring and life support which must be provided by a team that can provide continuous titrated care.
PEGylated FGF-21 polypeptides are described in WO 2005/091944, which is incorporated by reference herein. The FGF-21 polypeptide described in WO 2005/091944 is a 181 amino acid polypeptide. The mature, wild-type, or native human FGF-21 sequence indicated as SEQ ID NO: 1 of WO 2005/091944 lacks a leader sequence. This human FGF-21 is highly identical to mouse FGF-21 (˜79% amino acid identity) and rat FGF-21 (˜80% amino acid identity). The human FGF-21 sequence presented as SEQ ID NO: 5 herein is the same sequence as SEQ ID NO: 1 of WO 05/091944. This sequence has a single nucleotide polymorphism (SNP) with leucine (L) at position 146. One of ordinary skill in the art could readily use alternative mammalian FGF-21 polypeptide sequences or analogs, muteins, or derivatives that have sufficient homology to the human FGF-21 sequences for the uses described herein.
The human FGF-21 sequence presented as SEQ ID NO: 1 herein has a single nucleotide polymorphism (SNP) with proline (P) at position 146. A N-terminal His tag version of SEQ ID NO: 1 is shown as SEQ ID NO: 2 herein.
WO 2005/091944 describes the covalent attachment of one or more molecules of PEG to particular residues of an FGF-21 compound. The resulting compound was a biologically active, PEGylated FGF-21 compound with an extended elimination half-life and reduced clearance when compared to that of native FGF-21. The PEG molecules were covalently attached to cysteine or lysine residues. Substitutions were made at various positions with cysteine to allow attachment of at least one PEG molecule. PEGylation at one or more lysine residues (56, 59, 69, and 122) was described.
PEGylated FGF-21 compounds would be useful in treating subjects with disorders, including, but not limited to, type 2 diabetes, obesity, insulin resistance, hyperinsulinemia, glucose intolerance, hyperglycemia, and metabolic syndrome. It would be particularly advantageous to have PEGylated FGF-21 compounds that could increase efficacy by allowing for a longer circulating half-life and that would require fewer doses, increasing both the convenience to a subject in need of such therapy and the likelihood of a subject's compliance with dosing requirements. Metabolic syndrome can be defined as a cluster of at least three of the following signs: abdominal fat—in most men, a 40-inch waist or greater; high blood sugar—at least 110 milligrams per deciliter (mg/dL) after fasting; high triglycerides—at least 150 mg/dL in the bloodstream; low HDL—less than 40 mg/dL; and, blood pressure of 130/85 of higher.
Covalent attachment of the hydrophilic polymer poly(ethylene glycol), abbreviated PEG, is a method of increasing water solubility, bioavailability, increasing serum half-life, increasing therapeutic half-life, modulating immunogenicity, modulating biological activity, or extending the circulation time of many biologically active molecules, including proteins, peptides, and particularly hydrophobic molecules. PEG has been used extensively in pharmaceuticals, on artificial implants, and in other applications where biocompatibility, lack of toxicity, and lack of immunogenicity are of importance. In order to maximize the desired properties of PEG, the total molecular weight and hydration state of the PEG polymer or polymers attached to the biologically active molecule must be sufficiently high to impart the advantageous characteristics typically associated with PEG polymer attachment, such as increased water solubility and circulating half life, while not adversely impacting the bioactivity of the parent molecule.
PEG derivatives are frequently linked to biologically active molecules through reactive chemical functionalities, such as lysine, cysteine and histidine residues, the N-terminus and carbohydrate moieties. There has been research on the formulation of a therapeutic FGF-21 compound, but it has been problematic for many reasons, one of which is because proteins and other molecules often have a limited number of reactive sites available for polymer attachment. Often, the sites most suitable for modification via polymer attachment play a significant role in receptor binding, and are necessary for retention of the biological activity of the molecule. As a result, indiscriminate attachment of polymer chains to such reactive sites on a biologically active molecule often leads to a significant reduction or even total loss of biological activity of the polymer-modified molecule. R. Clark et al., (1996), J. Biol. Chem., 271:21969-21977. To form conjugates having sufficient polymer molecular weight for imparting the desired advantages to a target molecule, prior art approaches have typically involved random attachment of numerous polymer arms to the molecule, thereby increasing the risk of a reduction or even total loss in bioactivity of the parent molecule.
Reactive sites that form the loci for attachment of PEG derivatives to proteins are dictated by the protein's structure. Proteins, including enzymes, are composed of various sequences of alpha-amino acids, which have the general structure H2N—CHR—COOH. The alpha amino moiety (H2N—) of one amino acid joins to the carboxyl moiety (—COOH) of an adjacent amino acid to form amide linkages, which can be represented as —(NH—CHR—CO)n—, where the subscript “n” can equal hundreds or thousands. The fragment represented by R can contain reactive sites for protein biological activity and for attachment of PEG derivatives.
For example, in the case of the amino acid lysine, there exists an —NH2 moiety in the epsilon position as well as in the alpha position. The epsilon —NH2 is free for reaction under conditions of basic pH. Much of the art in the field of protein derivatization with PEG has been directed to developing PEG derivatives for attachment to the epsilon —NH2 moiety of lysine residues present in proteins. “Polyethylene Glycol and Derivatives for Advanced PEGylation”, Nektar Molecular Engineering Catalog, 2003, pp. 1-17. These PEG derivatives all have the common limitation, however, that they cannot be installed selectively among the often numerous lysine residues present on the surfaces of proteins. This can be a significant limitation in instances where a lysine residue is important to protein activity, existing in an enzyme active site for example, or in cases where a lysine residue plays a role in mediating the interaction of the protein with other biological molecules, as in the case of receptor binding sites.
A second and equally important complication of existing methods for protein PEGylation is that the PEG derivatives can undergo undesired side reactions with residues other than those desired. Histidine contains a reactive imino moiety, represented structurally as —N(H)—, but many chemically reactive species that react with epsilon —NH2 can also react with —N(H)—. Similarly, the side chain of the amino acid cysteine bears a free sulfhydryl group, represented structurally as —SH. In some instances, the PEG derivatives directed at the epsilon —NH2 group of lysine also react with cysteine, histidine or other residues. This can create complex, heterogeneous mixtures of PEG-derivatized bioactive molecules and risks destroying the activity of the bioactive molecule being targeted. It would be desirable to develop PEG derivatives that permit a chemical functional group to be introduced at a single site within the protein that would then enable the selective coupling of one or more PEG polymers to the bioactive molecule at specific sites on the protein surface that are both well-defined and predictable.
In addition to lysine residues, considerable effort in the art has been directed toward the development of activated PEG reagents that target other amino acid side chains, including cysteine, histidine and the N-terminus. See, e.g., U.S. Pat. No. 6,610,281 which is incorporated by reference herein, and “Polyethylene Glycol and Derivatives for Advanced PEGylation”, Nektar Molecular Engineering Catalog, 2003, pp. 1-17. A cysteine residue can be introduced site-selectively into the structure of proteins using site-directed mutagenesis and other techniques known in the art, and the resulting free sulfhydryl moiety can be reacted with PEG derivatives that bear thiol-reactive functional groups. This approach is complicated, however, in that the introduction of a free sulfhydryl group can complicate the expression, folding and stability of the resulting protein. Thus, it would be desirable to have a means to introduce a chemical functional group into FGF-21 that enables the selective coupling of one or more PEG polymers to the protein while simultaneously being compatible with (i.e., not engaging in undesired side reactions with) sulfhydryls and other chemical functional groups typically found in proteins.
As can be seen from a sampling of the art, many of these derivatives that have been developed for attachment to the side chains of proteins, in particular, the —NH2 moiety on the lysine amino acid side chain and the —SH moiety on the cysteine side chain, have proven problematic in their synthesis and use. Some form unstable linkages with the protein that are subject to hydrolysis and therefore decompose, degrade, or are otherwise unstable in aqueous environments, such as in the bloodstream. Some form more stable linkages, but are subject to hydrolysis before the linkage is formed, which means that the reactive group on the PEG derivative may be inactivated before the protein can be attached. Some are somewhat toxic and are therefore less suitable for use in vivo. Some are too slow to react to be practically useful. Some result in a loss of protein activity by attaching to sites responsible for the protein's activity. Some are not specific in the sites to which they will attach, which can also result in a loss of desirable activity and in a lack of reproducibility of results. In order to overcome the challenges associated with modifying proteins with poly(ethylene glycol) moieties, PEG derivatives have been developed that are more stable (e.g., U.S. Pat. No. 6,602,498, which is incorporated by reference herein) or that react selectively with thiol moieties on molecules and surfaces (e.g., U.S. Pat. No. 6,610,281, which is incorporated by reference herein). There is clearly a need in the art for PEG derivatives that are chemically inert in physiological environments until called upon to react selectively to form stable chemical bonds.
Recently, an entirely new technology in the protein sciences has been reported, which promises to overcome many of the limitations associated with site-specific modifications of proteins. Specifically, new components have been added to the protein biosynthetic machinery of the prokaryote Escherichia coli (E. coli) (e.g., L. Wang, et al., (2001), Science 292:498-500) and the eukaryote Saccharomyces cerevisiae (S. cerevisiae) (e.g., J. Chin et al., Science 301:964-7 (2003)), which has enabled the incorporation of non-genetically encoded amino acids to proteins in vivo. A number of new amino acids with novel chemical, physical or biological properties, including photoaffinity labels and photoisomerizable amino acids, photocrosslinking amino acids (see, e.g., Chin, J. W., et al. (2002) Proc. Natl. Acad. Sci. U.S.A 99:11020-11024; and, Chin, J. W., et al., (2002) J. Am. Chem. Soc. 124:9026-9027), keto amino acids, heavy atom containing amino acids, and glycosylated amino acids have been incorporated efficiently and with high fidelity into proteins in E. coli and in yeast in response to the amber codon, TAG, using this methodology. See, e.g., J. W. Chin et al., (2002), Journal of the American Chemical Society 124:9026-9027; J. W. Chin, & P. G. Schultz, (2002), ChemBioChem 3(11):1135-1137; J. W. Chin, et al., (2002), PNAS United States of America 99:11020-11024; and, L. Wang, & P. G. Schultz, (2002), Chem. Comm., 1:1-11. All references are incorporated by reference in their entirety. These studies have demonstrated that it is possible to selectively and routinely introduce chemical functional groups, such as ketone groups, alkyne groups and azide moieties, that are not found in proteins, that are chemically inert to all of the functional groups found in the 20 common, genetically-encoded amino acids and that may be used to react efficiently and selectively to form stable covalent linkages.
The ability to incorporate non-genetically encoded amino acids into proteins permits the introduction of chemical functional groups that could provide valuable alternatives to the naturally-occurring functional groups, such as the epsilon —NH2 of lysine, the sulfhydryl —SH of cysteine, the imino group of histidine, etc. Certain chemical functional groups are known to be inert to the functional groups found in the 20 common, genetically-encoded amino acids but react cleanly and efficiently to form stable linkages. Azide and acetylene groups, for example, are known in the art to undergo a Huisgen [3+2] cycloaddition reaction in aqueous conditions in the presence of a catalytic amount of copper. See, e.g., Tornoe, et al., (2002) J. Org. Chem. 67:3057-3064; and, Rostovtsev, et al., (2002) Angew. Chem. Int. Ed. 41:2596-2599. By introducing an azide moiety into a protein structure, for example, one is able to incorporate a functional group that is chemically inert to amines, sulfhydryls, carboxylic acids, hydroxyl groups found in proteins, but that also reacts smoothly and efficiently with an acetylene moiety to form a cycloaddition product. Importantly, in the absence of the acetylene moiety, the azide remains chemically inert and unreactive in the presence of other protein side chains and under physiological conditions.
The present invention addresses, among other things, problems associated with the activity and production of FGF-21 polypeptides, and also addresses the production of an FGF-21 polypeptide with improved biological or pharmacological properties, such as improved therapeutic half-life.